Dynamically and Efficiently Forming Hierarchical Tunnels

1. A method, comprising: using a hierarchical tunnel that encapsulates a plurality of child tunnels along a shared path segment, the shared path segment extending from a head-end node across one or more intermediate nodes to a tail-end node; and refreshing a state of a child tunnel of the plurality of child tunnels encapsulated within the hierarchical tunnel by sending, by the head-end node, one or more refresh messages along the child tunnel that include a request that the one or more intermediate nodes remove the state of the child tunnel without sending error messages, and sending, by the head-end node, one or more encapsulated refresh messages within the hierarchical tunnel that cause the tail-end node to continue propagation of refresh messages along the child tunnel.

2. The method of claim 1 , wherein the request causes resources used by the child tunnel to be freed at the one or more intermediate nodes.

3. The method of claim 1 , wherein the one or more refresh messages are one or more Resource ReSerVation Protocol (RSVP) Path messages and the error messages are RSVP PathErr or PathTear messages.

4. The method of claim 3 , wherein the request is embodied as an extension object field of the one or more RSVP Path messages.

5. The method of claim 1 , wherein the one or more encapsulated refresh messages include a hop-by-hop path of the child tunnel with the one or more intermediate nodes removed such that the tail-end node appears as a next hop.

6. The method of claim 5 , wherein the one or more encapsulated refresh messages are one or more ReSerVation Protocol (RSVP) Path messages and the hop-by-hop path is an explicit route object (ERO) contained in the one or more RSVP Path messages.

7. The method of claim 1 , wherein the one or more refresh messages and the one or more encapsulated refresh messages are sent simultaneously.

8. The method of claim 1 , wherein the request indicates the removal of the state of the child tunnel should be delayed such that the state is not removed until the hierarchical tunnel is established.

9. The method of claim 1 , wherein the using further comprises establishing the hierarchical tunnel by: determining a set of attribute groups (AGs) of tunnels, wherein an AG is a group of compatible attributes among tunnels; determining a set of tunnels that belong to a particular AG and that follow the shared path segment; and using the set of tunnels as the plurality of child tunnels.

10. The method of claim 1 , wherein the head-end node comprises one or more network interfaces, one or more processors and a memory.

11. An apparatus, comprising: one or more network interfaces coupled to child tunnels, the child tunnels encapsulated by a hierarchical tunnel along a shared path segment that extends from the apparatus across one or more intermediate nodes to a tail-end node; one or more processors coupled to the one or more network interfaces and configured to execute one or more software processes; and a memory configured to store a software process executable by each processor, the software process configured, when executed, to: send one or more refresh messages along the child tunnel that include a request that the one or more intermediate nodes remove the state of the child tunnel without sending error messages, and send one or more encapsulated refresh messages within the hierarchical tunnel that cause the tail-end node to continue propagation of refresh messages along the child tunnel.

12. The apparatus of claim 11 , wherein the request causes resources used by the child tunnel to be freed at the one or more intermediate nodes.

13. The apparatus of claim 11 , wherein the one or more refresh messages are one or more Resource ReSerVation Protocol (RSVP) Path messages and the error messages are RSVP PathErr or PathTear messages.

14. The apparatus of claim 13 , wherein the request is embodied as an extension object field of the one or more RSVP Path messages.

15. The apparatus of claim 11 , wherein the one or more encapsulated refresh messages include a hop-by-hop path of the child tunnel with the one or more intermediate nodes removed such that the tail-end node appears as a next hop.

16. The apparatus of claim 15 , wherein the one or more encapsulated refresh messages are one or more ReSerVation Protocol (RSVP) Path messages and the hop-by-hop path is an explicit route object (ERO) contained in the one or more RSVP Path messages.

17. The apparatus of claim 11 , wherein the software processes are further configured, when executed, to send the one or more refresh messages and the one or more encapsulated refresh messages simultaneously.

18. The apparatus of claim 11 , wherein the request indicates the removal of the state of the child tunnel should be delayed such that the state is not removed until the hierarchical tunnel is established.

19. The apparatus of claim 11 , wherein the software processes are further configured, when executed, to: determine a set of attribute groups (AGs) of tunnels, wherein an AG is a group of compatible attributes among tunnels, determine a set of tunnels that belong to a particular AG and that follow the shared path segment, and use the set of tunnels as the plurality of child tunnels.

20. One or more non-transitory computer-readable media encoded with software that when executed is operable to: use a hierarchical tunnel that encapsulates a plurality of child tunnels along a shared path segment, the shared path segment extending from a head-end node across one or more intermediate nodes to a tail-end node; and refresh a state of a child tunnel of the plurality of child tunnels encapsulated within the hierarchical tunnel by transmission of one or more refresh messages along the child tunnel that include a request that the one or more intermediate nodes remove the state of the child tunnel without sending error messages, and transmission of one or more encapsulated refresh messages within the hierarchical tunnel that cause the tail-end node to continue propagation of refresh messages along the child tunnel.